In the aeronautical field, the weight and the noise of the embedded components are important parameters for which reductions are sought. To this end, it is possible to use electrical conductors made of aluminum, lighter than copper, for a use of the electrical component at a given power. The ductility of aluminum is much lower than that of copper. Consequently, aluminum in sheet form is often used, that is wound to produce coils.
The coils are wound around closed magnetic circuits to best guide the magnetic flux. Magnetic circuits produced in two parts are commonly used. The coil or coils are produced outside of the magnetic circuit, then placed therein. Once this operation is completed, the two parts of the magnetic circuit are assembled to close the circuit. The junction between the two parts forms an air gap. It is difficult to make the two surfaces forming the air gap strictly parallel: there remains a low deviation between the two parts that is difficult to eliminate. The surfaces of the two parts intended to come into contact can be ground in order to improve the surface condition at the junction. It is also possible to band the magnetic circuit by means of a strip surrounding it to close it. The banding force contributes to further reducing the air gap.
Nevertheless, the electrical current circulating in the coils can generate mechanical vibrations in the device. These vibrations tend to separate the two parts of the magnetic circuit to reform an air gap. The vibrations can also tend to loosen the mechanical securing of the different parts of the magnetic circuit, which tends to allow the amplitude of the vibrations to increase throughout the life of the coil. At the same time, the induction device heats up during its use. The temperature difference of the induction device between use and rest can lead to an expansion of the magnetic circuit and the appearance of a deviation in the air gap.
Moreover, the vibrations described previously tend also to generate noise which can be a nuisance. The constructors, for example in aeronautics, demand increasingly lower sound nuisance levels.
To mitigate this problem, there are electromagnetic induction devices and transformers in which the magnetic circuit does not have an air gap. The electrically conductive coil must be wound around the magnetic circuit: a device for this winding is described in the patent FR 2939559. This device uses a sleeve, also called duct, of circular internal section, assembled from two parts around the magnetic circuit. The electrical conductor is first of all attached to this sleeve. A driving means then rotates this sleeve, via a sleeve engaging means. The sheet or sheets of electrical conductor are then wound around the sleeve.
Another known technical problem with induction devices lies in the occurrence of eddy currents in the magnetic circuit, leading to a loss of energy due to the electrical resistance of the magnetic material, if the material is an electrical conductor. This problem is conventionally mitigated by the production of a layered laminated magnetic circuit: flat plates of magnetic material, electrically insulated from one another by an electrically insulating material, such as lacquer or certain types of glue, are superposed one on top of the other. This super positioning can also be obtained by winding a plate. Each layer of the winding is then separated by an electrically insulating material.
The magnetic material used in the magnetic circuit is often a soft magnetic material, to avoid the losses of energy by hysteresis upon the imposition of variable magnetic fluxes. The circuit obtained makes it possible to limit the occurrence of the eddy currents, but the section of the magnetic circuit obtained, by using this production method, is rectangular.
The difference in form between the circular section of the sleeve and the rectangular section of the magnetic circuit limits the efficiency of the energy coupling between the coil and the magnetic circuit and leads to losses in the use of the transformer.
Another limitation of the device is linked to the losses by Joules' effect. They can reach high temperatures (typically above 100° C.) on the device and thus limit its use. Different cooling means are generally used to reduce the temperature of the electromagnetic induction devices: by liquid contact or by solid contact with a cold reservoir.
The invention aims to overcome at least one of the abovementioned drawbacks of the prior art.